<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script>
        window.onload=function(){
            alert(document.childNodes[1].tagName);//tagName就是标签名
            //HTML
            alert(document.childNodes.tagName);
            //!叹号
            //document就是HTML文档看不见的父级
        }
    </script>
</head>
<body>
    
</body>
</html>